I have had guineas for 4 years now and have never had any run off or head for the hills. The first ones you get need to be confined for about 4 weeks to learn where home is, but after that, it's pretty easy. Mine free range all day and go in the coop at night. My guineas love white millet, so all I have to do is call "chick, chick, chick!" a shake the millet bag and they will come running from wherever they are at. I let my guineas hatch their own eggs and raise their own keets and have been very pleased with the results. Although not all guineas owners agree with doing this I have found that it works well for me.
As for getting stressed, if they had plenty of room to roam, perches to roost on, and protection from the weather and predators, I would think they would do ok.
Thank you for the advice!